Affiliations: Faculty of Applied Sciences, Delft University of
Technology, Lorentzweg 1, P. O. Box 5046, 2600 GA, Delft, The Netherlands
Abstract: A time-dependent Reynolds-average-Navier-Stokes (TRANS) method is
applied to capture and analyze the large-scale coherent structure in
Rayleigh-Bénard (RB) convection over a flat and wavy bottom wall at a
range of Rayleigh numbers. The method can be regarded as a Very Large Eddy
Simulation (VLES) in which the unresolved random motion is modelled using a
low-Re-number k-ϵ-&b.thetas;² algebraic stress/flux
single-point closure model. The large scale motion, which is the major mode of
heat and momentum transfer in the bulk central region, is fully resolved by the
time solution. In contrast to LES, the contribution of both modes to the
turbulent fluctuations are of the same order of magnitude. The approach was
assessed by comparison with the Direct Numerical Simulations (DNS) and
experimental data using several criteria: visual observation of the large
structure morphology, different structure identification criteria, and
long-term averaged mean flow and turbulence properties. A visible similarity
with large structures in DNS was observed, confirming the suitability of TRANS
approach to reproduce the flows dominated by large coherent motions.